EXsoccer1921

iTrader: (14)

thats why i posted the sheet to show the torque curve a full 3" gives...

*shrug*

05Slowline

iTrader: (2)

I see. too bad you didn't have a 2.5" to swap on and see the difference .

EXsoccer1921

iTrader: (14)

you are right on that one. but oh well. if you really want you can go through the dyno thread and see what other 2.8s did and look at the graphs if they had 2.5" haha cause i don't feel like doing that. but its still 250 peak and a damn nice curve. my next cobalt will be comparing a lot of things so we'll see what kinda curves we can get out of it then

elite_Cyborg

iTrader: (6)

So who wants to swap?

ItalianJoe1

iTrader: (10)

Exhaust theory is always the same, you have to plan on your displacement vs. engine speed and a guesstimate of the VE to find an ideal primary volume (length and diameter). The difference on a forced induction engine is that once you go positive on the intake manifold side, the effect of the exhaust pulse pulling fresh charge into the cyl is almost nil, so it matters little. After that point, exhaust just needs to get the spent charge out of the cyl head as quickly as possible. Merge collectors still help, as they keep the charge speed up in the pipes if designed correctly. A well planned exhaust can easily result in a negative pressure above the exhaust valve when it opens, and anyone can realize that you will use less power to push the exhaust into a vacuum than you will into a pressurized area. Just a couple in/hg either way makes a large difference.

I'll try to find the book I read last, it was an older book but had a really solid way of displaying the theory, made it nice very straightforward.

So, on a TVS car with far more airflow, why did switching from a GMPP cat-back to a full 3" only net 2whp?

EXsoccer1921

iTrader: (14)

**** if i know i ain't a genius and i don't try to be. i haven't had any experience with a tvs. he was asking about the area under the curve instead of just peak numbers so i referenced my dyno sheet so he could see the curve. but if you saw a difference in peak numbers, you probably saw a good change in the curve as well. so apparently a 3" flows better than the gmpp on a tvs?

ItalianJoe1

iTrader: (10)

Just barely. Everyone told him he was losing power due to the smallish exhaust. He changed it and didn't gain ****. Even with a ton more airflow than you're at.

EXsoccer1921

iTrader: (14)

just proves my point that you can switch to a 3" sooner than people think. a 2.5 can/does work fine. but a 3" can generally make more power and torque under the curve

oh well, idc what other people use lol. my setup worked great and the only thing i think i'll change is testing out a 2.5" vs 3" on the same setup and see what happens then use the appropriate one.

elite_Cyborg

iTrader: (6)

I'm pretty sure i would pick up atleast 5hp with 3 inch

EXsoccer1921

iTrader: (14)

riley what exhaust do you have, i'm comin up to kc after i get back from NY to give cody my h/e. i might trade ya for yours +cash

elite_Cyborg

iTrader: (6)

Megan Racing It sounds Decent when my dp isn't leaking

EXsoccer1921

iTrader: (14)

fart can ftw!! hahah

ralliartist

pacesetter header with burns collector > all

on a ss/sc

EXsoccer1921

iTrader: (14)

i'm still waiting for numbers on an ottp longtube catless with 3" exhaust....but i know thats never gonna happen

ralliartist

yea, you and the rest of the world. lol.

EXsoccer1921

iTrader: (14)

haha exactly. i'm gonna be pissed if the wait is so long that i end up being the first to try it

ralliartist

Research I've done lately has said that Short Large Primaries with a big collector work best on a supercharged engine.

I really think a Pacesetter with a Burns collector is going to be about the best you can get.

ecot3c inside

iTrader: (11)

Thanks. Ya, the shop threw that one out..

this is kind of like the the argument 'do I fill the tire according to a tad below max on the sidewall or do I look inside the door jam'.

ralliartist

uh, no it's not.

ecot3c inside

iTrader: (11)

ya it is

Render2009

iTrader: (4)

so if i put full hahn on my stock ss.. im gonna f it up?

05Slowline

iTrader: (2)

Lol. You really don't need a 3" on these unless you are turbo or a high hp tvs.....it's not a total buzzkiller but its retarded.